| 27 October 1930 |
United States
|
Mathematics
|
West models the shape of Earth
|
| 27 October 1930 |
United States
|
Mathematics
|
Satellite geodesy requires sustained mathematical labour
|
| 27 October 1930 |
United States
|
Mathematics
|
Recognition comes late for a Black woman mathematician
|
| 18 February 1930 |
United States
|
Astronomy
|
Tombaugh identifies Pluto
|
| 18 February 1930 |
United States
|
Astronomy
|
A blink comparator reveals a distant object
|
| 18 February 1930 |
United States
|
Astronomy
|
Lowell Observatory finds a new solar-system body
|
| 18 February 1930 |
United States
|
Astronomy
|
Pluto's discovery begins a new classification story
|
| 25 August 1925 |
United States
|
Racism
|
Sleeping car porters organize an independent union
|
| 2 June 1924 |
United States
|
Racism
|
The Indian Citizenship Act grants citizenship without ending colonial control
|
| 5 October 1923 |
United States
|
Astronomy
|
Hubble begins a key Andromeda exposure
|
| 5 October 1923 |
United States
|
Astronomy
|
An Andromeda plate captures a future clue
|
| 5 October 1923 |
United States
|
Astronomy
|
Mount Wilson photographs individual stars
|
| 5 October 1923 |
United States
|
Astronomy
|
A dated image enters the distance debate
|
| 9 April 1921 |
United States
|
Mathematics
|
Mary Jackson is born
|
| 9 April 1921 |
United States
|
Mathematics
|
Jackson studies supersonic airflow
|
